The present invention is related to a method for determining a characteristic curve for an electric variable of a wind energy plant, wherein the characteristic curve contains characteristic values of the electric variable as a function of different values of the wind. Moreover, the present invention is related to an apparatus for determining a characteristic curve for an electric variable of a wind energy plant, wherein the characteristic curve contains characteristic values of the electric variable as a function of different values of the wind.
With increasing capacity of wind energy plants and the combination thereof to wind parks, there is a demand to be able to regulate or control, respectively, the feeding of electric power into the grid. For this purpose, it is known to operate wind energy plants and wind parks with a throttled power, when no higher power can or is to be fed into the grid. In a throttled operation of the wind energy plant, there is a demand to determine the existing control reserve of an electric variable, like the effective power of the wind energy plant for instance. Therefore, characteristic curves for electric variables are established for wind energy plants, before the distribution of the plant for instance, wherein the characteristic curves contain characteristic values of the electric variable as a function of different values of the wind, different wind velocities for instance. Such characteristic curves are also designated as predetermined characteristic curves.
For instance, such characteristic curves can be calculated or preferably experimentally established for a reference wind energy plant of the respective plant type by determining characteristic values of the electric variable for the reference plant at different wind velocities. In doing so, a problem is that depending on production variations for instance, differences of the characteristic curve of an individual wind energy plant with respect to the characteristic curve established for the reference wind energy plant may result. Thus, higher as well as lower characteristic values for the electric variable than indicated in the predetermined characteristic curve may result for an individual wind energy plant.
Therefore, it has been proposed to establish an individual characteristic curve for each wind energy plant before the distribution. Admittedly, it came out that depending on geographic or other conditions of the operation of the wind energy plant on the later installation site, for instance, other characteristic values of the electric variable than have been established for the individually predetermined characteristic curve may result in turn. Therefore, the predetermined characteristic curve is not always sufficiently reliable.
It has furthermore been tried to establish the predetermined characteristic curve experimentally not before the wind energy plant is installed at the installation location. A disadvantage of this procedure is however that the characteristic curve of the wind energy plant is available only after a relatively long measuring period, i.e. when characteristic values of the electric variable could have been measured for a sufficient number of different wind velocities. Through this, the start-up of the wind energy plant in its full extent is delayed.
Therefore, the present invention is based on the objective to provide a method and an apparatus of the kind indicated in the beginning, by which a more reliable characteristic curve for an electric variable of a wind energy plant can be established without that delays in the start-up of the wind energy plant occur.